1. Field of the Invention
This invention relates to a code reader capable of reading data which the code means rapidly and correctly, even when a part of a code is, for example, defective or dirty.
2. Description of the Related Art
Heretofore, there is known a code reader for illuminating the code and reading the meaning of the code as data therefrom, the code in which all data are separated into at least two patterns such as a first partial code pattern and a second partial code pattern and a plurality of discriminating elements are arranged as such that the first and the second partial code patterns can be distinguished.
For example, in a bar code symbol, as shown in FIG. 11, a left character bar as a code pattern is disposed between a left guard bar as an end bar and a center bar as a discriminating element, and a right data character bar as a code pattern and a modular check character are disposed between the center bar and a right guide bar as an end bar. Data is given according to the width and space of the bar of the bar code. The code reader reads the width and space of the bar by illuminating the bar code symbol and obtains data.
However, for some instance such as when a bar code symbol becomes dirty or defective or when a harmful reflection light enters, the conventional code reader is unable to read the code. In order to read the code, the reading procedure must be taken repeatedly. Thus, there is present such a problem as that the reading work is inconvenient.
To solve this problem, a code reader is proposed as disclosed in Japanese patent publication No. 54-34618 and Japanese patent publication No. 54-4208, in which illumination scanning places L.sub.1 and L.sub.2 are intendedly changed on a bar code in order to read a code meaning data. However, the code reader disclosed in Japanese patent publication Nos. 54-34618 and 54-4208 are constituted as such that the code meaning data is unable to be read as long as all data are not regularly read. Therefore, in order to read the code meaning data, the data must be read by illuminating only a place of the code where the code does not become dirty. For example, when a bar code symbol 8 gets dirty or defective as shown in FIGS. 12 and 13, a scanning line crosses a dirty part at any scanning place as shown in scannings l.sub.1 and l.sub.2. Therefore, the bar code meaning data is unable to read at all.
Moreover, in the case of an enlarged bar code symbol, only a part of the bar code symbol can be read as data in such a near distance shorter than the arrangement width of the bar code. Therefore, the all data cannot be read, even if the reading operation is repeated many times.